Geocomposite system for roads and bridges and construction method

ABSTRACT

A geocomposite system for increasing the service life of roads, bridges, or the like, includes a geocomposite layer having a geomembrane disposed between two geotextile backings, a structural layer for supporting the geocomposite layer, and a base layer formed on top of the geocomposite layer. The geomembrane is impermeable and the geotextile backings are sufficiently porous to provide a wicking action of moisture or liquid laterally along the geomembrane and out of the geocomposite system to prevent moisture or liquid damage. The geomembrane prevents the intrusion of liquids including deicing salts into the structural layers of roads, bridges, or the like abating deterioration in the structural layers such as corrosion of reinforcing steel. The geocomposite layer is bonded to and conforms to the structural layer, thus reducing reflective, shrinkage and fatigue cracking and increasing the structural capacity of the road or bridge. Preferably, the geomembrane is an extruded polyvinylchloride web and the geotextile backings are fabricated of a mat of non-woven polyester fibers. The geotextile backings are heat coupled to the geomembrane, preferably using a calendaring process. The geocomposite layer is also bonded to the base layer. In the related method, the geocomposite system is constructed by fabricating the geocomposite layer, applying a tack coat to the structural layer, placing the geocomposite layer with the geotextile backing down on the prepared structural layer, rolling the geocomposite to provide conformity with the structural layer, applying a tack coat to the other geotextile backing and forming and bonding the base layer on the geocomposite layer.

TECHNICAL FIELD

[0001] The present invention relates generally to geocomposite systems,and more particularly to using a geocomposite layer in the constructionof roads and bridges.

BACKGROUND OF THE INVENTION

[0002] The United States has a public roadway infrastructure of morethan 6.2 million kilometers with more than 575,000 bridges which istraveled by more than 2.4 trillion vehicle-miles per year. Approximately3.8 million kilometers of the system are paved road, 96% of these pavedroads have flexible, or hot-mix asphalt, pavements. It is estimated thatapproximately one sixth of the more than 90 billion dollars spentannually by U.S. governmental agencies to enhance, rehabilitate, andmaintain the public roadway infrastructure is spent on constructing andmaintaining these paved roads.

[0003] Considering the magnitude of this type of annual investment, thepotential savings from developing improved and longer lasting pavementsystems is substantial. For example, if the service life of a newpavement system is extended by three years, i.e., twenty percentconsidering the average life of a pavement system is 15 years, thesavings in hot-mix asphalt alone is estimated to be three billiondollars per year. Furthermore, the labor cost savings are estimated tobe at least ten times this amount.

[0004] Another substantial expense involving the public highwayinfrastructure is the rehabilitation and maintenance costs associatedwith the corrosion of reinforcing steel in bridge decks. In 1991, thebacklog of public bridge repair and maintenance costs was estimated tobe 78 billion dollars. It is also estimated that 40% of the 575,000bridges are structurally or functionally obsolete with reinforcing steelcorrosion being the major cause of deterioration at more than 31 billiondollars.

[0005] In order to stem the overwhelming costs associated with theenhancement, rehabilitation, and maintenance of the public highwayinfrastructure, several techniques have been developed which attempt toprevent or deter the deterioration and eventual breakdown of roads andthe corrosion of reinforcing steel in bridges. For example, severaltechniques were used to abate corrosion in bridge decks including theuse of sealers, coated reinforcing bars, cathodic protection, lowpermeability concrete, and waterproofing membranes, among others.

[0006] Possibly the most popular of these techniques is shown in oneform in U.S. Pat. No. 4,362,780 to Marzocchi et al., wherein a singlethickness fiber web is asphalt impregnated and laid between layers ofthe pavement system to impede the downward migration of water (or otherliquids) into the roadbed or the bridge deck. Although successful inreducing the downward migration of some moisture, the web in the '780patent falls short in several functional areas, such as the ability tolaterally drain the water away and providing a cushioning effect toalleviate weather and traffic related damage.

[0007] Accordingly, while the use of impregnated fiber webs is generallyknown in the art of constructing roads and bridges, to date no one hasrecognized and adequately addressed the advantages of providing aprefabricated, composite layer, including an impermeable membrane. Thus,there is a need to provide an improved geocomposite system to extend theservice life of roads, bridges, or the like, and an improved method ofconstruction with such a composite layer. The geocomposite system andmethod should make the best use of a flexible geomembrane combined withat least one geotextile backing to form a geocomposite layer to belocated between adjacent geocomposite layers. This geocomposite layer soconstructed should prove to provide water impregnability in a verticaldirection, but allow lateral drainage. Indeed, it is contemplated thatutilizing a flexible geomembrane, and geotextile backings on both sides,can best carry out these intended purposes. In addition, there should bea significant improvement in the structural capacity and cushioning ofthe road or bridge to withstand rigorous dynamic loading by traffic.Costly cracking and deterioration, including due to water, is to besignificantly reduced, and the life of the road or bridge significantlyextended.

SUMMARY OF THE INVENTION

[0008] Accordingly, the primary object of the present invention is toprovide an improved geocomposite system for extending the service lifeof roads, bridges, or the like by overcoming the limitations anddisadvantages of the prior art and adopting the improvement featurescontemplated above.

[0009] Another object of the present invention is to provide ageocomposite system wherein a geocomposite layer or web placed betweenan upper base layer and a lower structural layer of a roadway or bridgeeliminates the vertical migration of water.

[0010] A further object of the present invention is to provide ageocomposite layer having a geomembrane disposed between first andsecond geotextile backings, which have sufficient porosity to provide awicking action of water along both sides of the geomembrane and out ofthe geocomposite system.

[0011] It is still another object of the present invention to provide ageocomposite system of the type described, which provides cushioning soas to dissipate stress loads to a level supportable by the base layer,and thus to alleviate load-related cracking.

[0012] Still another object of the present invention is to provide ageocomposite system utilizing a flexible and cushioned geomembranecapable of conforming to the base and structural layers of the roads andbridges.

[0013] Yet another object of the present invention is to provide ageocomposite layer of the type described having a geomembrane ofsufficient thickness to allow easy coupling of the geotextile backingsprior to installation in the road or bridge.

[0014] Another object of the present invention is to provide ageocomposite system including a geocomposite layer with thermalproperties sufficient to withstand the temperature of the base layer(e.g., hot-mix asphalt) during application of the base layer and havingsufficient thickness so that milling of a wear surface of the base layerwill not affect the geocomposite layer, thus allowing repair andreplacement of a portion of the wear surface.

[0015] Yet another and related object of the present invention is toprovide a method of constructing a geocomposite system for use in aroad, bridge, or the like, wherein the method includes fabricating ageocomposite layer, applying a tack coat to a structural layer of theroad or bridge, laying the geocomposite layer on the prepared structurallayer and rolling the geocomposite layer to insure conformity andcoupling, and applying a tack coat to the geotextile backing on theexposed side of the geocomposite layer, and forming a base layer on thegeocomposite layer.

[0016] Additional objects, advantages and other novel features of theinvention will be set forth in part in the description that follows andin part will become apparent to those skilled in the art uponexamination of the following or may be learned with the practice of theinvention. The objects and advantages of the invention may be realizedand obtained by means of the instrumentalities and combinationsparticularly pointed out in the appended claims.

[0017] To achieve the foregoing and other objects, and in accordancewith the purposes of this invention, an improved geocomposite system isprovided, and is contemplated to be utilized to increase the servicelife of roads, bridges, or the like. The geocomposite system includes ageocomposite layer disposed between and bonded to a structural layer anda base layer. More specifically, the geocomposite layer is securelybonded to each of the structural and the base layers by means of a tackcoat of a suitable adhesive. Within the broadest aspects of the presentinvention, the geocomposite layer provides a barrier against thepenetration or permeation of surface moisture or liquid into thestructural layer, as well as, upward migration of ground moisture orliquid into the base layer. Additionally, the geocomposite layer placedin between conforms to the base and structural layers such that the loadof passing vehicles is transferred through the geocomposite layer to thestructural layer efficiently by dissipating the applied stress.

[0018] In accordance with an important aspect of the present invention,the geocomposite layer includes a geomembrane disposed between first andsecond geotextile backings. The geotextile backings are fabricated of amat of non-woven polypropylene fibers or, in the present preferredembodiment, as a mat of non-woven polyester fibers. The geotextilebackings are securely adhered to the geomembrane through a heat couplingprocess, such as calendaring. Advantageously, this process allows thegeocomposite to be fabricated and quality tested prior to installationin the road or bridge. The geomembrane is preferably extruded having athickness in the range of 30 to 100 millimeters. In accordance with thebroader aspects of the present invention, the geomembrane can be formedutilizing various known processes and utilizing a material selected fromthe group consisting of polyvinylchloride, very flexible polyethylene,linear low density polyethylene, low density linear polyethylene,ethylene propylene diene terpolymer, or chlorosuphonated polyethylene.

[0019] In accordance with another feature of the invention, thegeomembrane is impermeable and the geotextile backings are sufficientlyporous to provide a wicking action of the moisture or liquid along thegeomembrane. Advantageously, the geotextile backings direct the moistureor liquid laterally, toward the edges of the road or bridge, while thegeomembrane prevents the migration of water between the base layer andthe structural layer. This is effective in preventing downwardpenetration or permeation of surface moisture into the structural layer,as well as, upward migration of ground moisture into the base layer.Overall, the combination of impeding and directing the flow of moistureor liquid is effective in preventing pooling within or between thelayers, dissipating pore water pressure, limiting soil movement, and/orproviding a moisture barrier that prevents water movement betweenlayers. Each of these scenarios, unless corrected by use of the presentinvention, is singly capable of causing minor to severe damage to a roador bridge.

[0020] The geomembrane is also flexible and elastic allowing thegeocomposite layer to substantially conform to the structural and baselayers of the road or bridge. Specifically, these positive conformalproperties allow loads created by constant traffic to be transferreddirectly, but in a cushioned fashion and thus more efficiently, to thestructural layer. The reduction or elimination of these undesirable loadconditions reduces the proliferation of reflective (or rebound),shrinkage and fatigue cracking in the road or bridge. Even morespecifically, the elasticity of the geomembrane allows the geomembraneto temporarily deform, thus cushioning and absorbing a significantportion of the lateral stresses imparted to the base layer by passingvehicles. This increases the effective overall tensile strength of thebase layer, and necessarily, the overall structural capacity anddurability of the road or bridge.

[0021] The geocomposite layer of the present invention preferablyincludes a geomembrane having a thickness in the range of between 30 and100 millimeters. Preferably, the thickness of the base layer issufficient to allow an upper portion to be removed and replaced withoutadversely affecting the geocomposite system, and specifically, the bondsbetween the geocomposite layer and the structural and base layers. It iscontemplated that the thickness of the base layer including the upperwear surface should be thick enough to allow milling of the wearsurface/base layer up to one-half inch above the geocomposite layer toaccommodate the later removal and replacement of a worn out wearsurface. Advantageously, this greatly reduces the costs associated withmaintenance of roads or bridges constructed in accordance with thepresent invention.

[0022] In accordance with the broadest aspects of the present invention,the geocomposite system can be utilized for new roads and bridges, orthe like. However, it is further contemplated that a specific form ofthe geocomposite system of the present invention may be further utilizedin the repair or rehabilitation of existing roads and bridges, and inknown trouble spots in new construction areas, such as in transitionareas between roads and bridges, or between train tracks at crossings,for example.

[0023] Preferably, the structural layer in a geocomposite systemutilized with a road includes a common sub-grade (road bed) or soilbase, a subbase, and a drainage layer of aggregate stone, for example.Alternatively, the structural layer of a geocomposite system utilizedwith a bridge may simply include a steel deck and/or a reinforcedconcrete deck. The base layer for either may include one or more layersof asphalt, including an asphalt wear surface.

[0024] In the related method, the geocomposite system is constructed byfirst fabricating the geocomposite layer. Preferably, the geomembrane isextruded and the geotextile backings are securely adhered to thegeomembrane through a heat coupling process, such as by calendaring,just after extrusion. Advantageously, this step is preferably carriedout prior to installation in the road or bridge. Necessarily, thisprovides a geocomposite of superior quality and uniformity thanheretofore achieved utilizing known prior art methods.

[0025] Next, the structural layer of the road or bridge is prepared toreceive the geocomposite layer, preferably by applying a tack coat of asuitable adhesive on top of the structural layer. The geocomposite layerwith a geotextile backing engaging the prepared structural layer absorbsa portion of the tack coat. A suitable force is applied to enhance theabsorption of the tack coat into the geotextile backing and to insuresubstantial conformity of the geocomposite layer with the structurallayer. An additional tack coat is applied to the top of the remainingexposed geotextile backing prior to forming the base layer. This insuresa secure bond between the geotextile backing and both of the base andstructural layers in either a road or bridge.

[0026] Still other objects of the present invention will become apparentto those skilled in this art from the following description whereinthere is shown and described a preferred embodiment of this invention,simply by way of illustration of one of the modes best suited to carryout the invention. As it will be realized, the invention is capable ofother different embodiments and its several details are capable ofmodification in various, obvious aspects all without departing from theinvention. Accordingly, the drawings and description will be regarded asillustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings incorporated in and forming a part ofthe specification, illustrate several aspects of the present inventionand together with the description serve to explain the principles of theinvention. In the drawings:

[0028]FIG. 1 is a cross sectional view of the geocomposite systemconstructed in accordance with the present invention, illustrating thegeocomposite layer within a road and indicating the drainage movement ofmoisture or liquid through the geotextile backings to one edge of thegeocomposite system and road edge;

[0029]FIG. 2 is a perspective exploded view of the geocomposite systemfor a road including the geocomposite layer, the preferred structurallayer, and the preferred base layer, all cut away in cross section forclarity;

[0030]FIG. 3 is a cross sectional view of the geocomposite system for abridge, again illustrating the geocomposite layer within thegeocomposite system, and indicating the lateral drainage of moisture orliquid through the geotextile backings to a suitable weep collectionchannel and exit passage;

[0031]FIG. 4 is a side cross sectional view showing the preferred methodof forming the geocomposite layer including heat coupling, utilizing acalendaring process, the geotextile backings to the geomembrane prior toinstallation in the road or bridge;

[0032]FIG. 5 is an illustrated view showing the preferred method ofconstructing the road or bridge including laying the geocomposite layerwith the geotextile backing on top of the prepared structural layer, andapplying a force, in the form of a roller, to enhance the absorption ofadhesive and to conform the geocomposite layer to the face of thestructural layer; and

[0033]FIG. 5a is a side enlarged cross sectional view taken from FIG. 5showing the spray application of the tack coats, the conforming effectof the applied force on the geocomposite layer, and the enhancedabsorption of the tack coat into the geotextile backing to form a securebond.

[0034] Reference will now be made in detail to the present preferredembodiment of the invention, an example of which is illustrated in theaccompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0035] Reference is now made to the drawings showing a geocompositesystem 10 forming a road in accordance with the present invention. Asindicated above, the particular preferred embodiment chosen toillustrate the invention, and best shown in FIG. 2, includes ageocomposite layer 12 disposed between a structural layer 14 and a baselayer 16 for extending the service life of the road. While the pavementsystem 10 is a preferred embodiment that takes full advantage of thepresent invention, it is to be understood that equivalent systems forextending the service life of roads, bridges, or the like are deemed tobe within the broadest aspects of the present invention.

[0036] As best shown in FIG. 1, the geocomposite layer 12 provides abarrier against the penetration or permeation of surface moisture orliquid (S) into the structural layer 14, as well as, upward migration ofground moisture or liquid (G) into the base layer 16. In other words,geocomposite layer 12 provides a barrier sufficient to prevent thevertical penetration or migration of moisture or liquid between thelayers of the geocomposite system 10. Additionally, the geocompositelayer 12, and specifically geotextile backings 20 and 22 retainsufficient porosity to provide a path based on wicking action for themoisture or liquid horizontally along geomembrane 18 out of thegeocomposite system 10 to a suitable stabilized edge drain system 24 forrelease beyond the shoulder of the road.

[0037] More specifically, the moisture or liquid (S or G) entering thegeocomposite system 10 is absorbed and flows or weeps through thegeotextile backings 20 and 22 to the edge drain system 24. The edgedrain system 24, in the present preferred embodiment, is a trough formedbeyond the edge of the emergency travel shoulder T of the pavementsystem 10. The semi-permeable stabilized aggregate stone and/or soilreceives the flow of moisture or liquid from the geotextile backings 20and 22 and directs it away from the road.

[0038] While the preferred edge drain system 24 is one commonly utilizedalong roadways and in other applications, it is to be understood thatother like systems for moving moisture or liquids away from thegeocomposite system 10 are deemed to be within the broadest aspects ofthe present invention. For example, a sub-surface geotextile wrappedpermeable pipe with spaced weep passages directed away from the shouldercould also perform the function.

[0039] The geocomposite layer 12 is both flexible and elastic.Advantageously, these properties allow the geocomposite layer 12 toconform to the structural layer 14 and the base layer 16. This allowsthe dynamic loading of passing vehicles to be transferred directlythrough the geocomposite layer 12 which acts as a stress absorptionlayer above the structural layer 14. This is of increased importance ingeocomposite systems wherein the structural layer is subjected to moresevere stress, or in transition areas such as between a road and abridge, for example. Absent these stress absorption properties, thegeocomposite layer 12 would transmit all loads into the structural layerfrom the passing vehicles. The reduction or elimination of theseundesirable stress loading conditions reduces the proliferation ofreflective (or rebound), fatigue and shrinkage cracking in roads orbridges.

[0040] The elasticity of the geomembrane allows the geomembrane 18 totemporarily deform up to 250 percent. This property allows a largeportion of the vertical stresses, but especially the lateral stresses,imparted to the base layer by passing vehicles to be cushioned, and ineffect absorbed by the geomembrane 18, thus preventing the transfer ofstresses to the structural layer 14. As noted above, this increases theoverall tensile strength of the structural layer 14 and the durabilityof the geocomposite system, and decreases the possibility of excessivesub grade deformation which may occur resulting in pavement cracking,rutting and other distresses.

[0041] As indicated above, the preferred geocomposite system 10 includesthe geocomposite layer 12 disposed between the structural layer 14 andthe base layer 16. Specifically, the structural layer 14 (shown in FIG.2) includes a sub grade 26, an aggregate layer 28, and a treatedaggregate layer 30. The base layer 16 comprises a base hot-mix asphaltcourse 32 and a wear hot-mix asphalt course 34. In this preferredembodiment, the geocomposite layer 12 is specifically disposed betweenthe upper most layer of the structural layer 14, i.e., it is between thetreated aggregate layer 30 and the base hot-mix asphalt course 32.

[0042] In accordance with the broadest aspects of the present invention,the structural layer 14 and the base layer 16 may include severaldistinct and varying layers and layer combinations dependent upon thespecific road or bridge application. While the preferred structurallayer 14 takes full advantage of the present invention, it is to beunderstood that other combinations and methods for forming thestructural layer 14 are deemed to be within the broadest aspects of thepresent invention. For example, the structural layer 14 may include morethan one aggregate or treated subbase layer. Further, the base layer 16could include an additional intermediate hot-mix asphalt layer, forexample, or it could be made semi-rigid, including a stabilizedaggregate layer and/or a concrete slab.

[0043] In addition to the various possible combinations of layersforming the structural layer 14 and the base layer 16, the placement ofthe geocomposite layer 12 within the geocomposite system 10 may alsovary dependent upon the specific required application. For instance, thegeocomposite layer 12 may alternatively be placed between the basehot-mix asphalt course 32 and the wear hot-mix asphalt course 34 withinthe base layer 16. This placement may be preferred for certain repair orrehabilitation purposes to reduce fatigue cracking due to its ability toabsorb stress/strain energy. Similarly, it could be placed between thesub grade 26 and the aggregate layer 28 within the structural layer 14for specific wetland applications.

[0044] As shown in FIG. 3, an alternate embodiment of the presentinvention includes a geocomposite system 40 for a bridge having ageocomposite layer 42 disposed between a structural layer 44 and a baselayer or overlay 46. In this preferred alternate embodiment, thestructural layer 44 includes a bridge deck 48 and a reinforced concretedeck 50, with or without reinforcement bars 52. The base layer 46, onthe other hand, is simply a hot-mix asphalt wear course 54. As in thegeocomposite system 10 utilized for roads, the geocomposite layer 42 andspecifically geotextile backings 56 and 58 provide a wicking action forlateral movement of moisture or liquids along the geomembrane 60 to thechannel 62 and weep passages 64.

[0045] As clearly shown in FIG. 3, the geocomposite system 40 isdesigned to extend the service life of the bridge primarily by providinga barrier against the penetration of surface moisture or liquid into thestructural layer 44. More specifically, the geocomposite system 40protects the bridge deck 48 and the reinforcement bars 52 from thecorrosive properties typically associated with moisture and otherliquids, such as chloride ions and other solutions, that result from useof ice and snow control materials in the colder climates and/orsplashing of seawater.

[0046] According to the present invention, the geocomposite layer 12 iscompletely fabricated and quality tested prior to installation in theroad geocomposite system 10 or bridge geocomposite system 40.Advantageously, this provides a superior quality and uniformity than washeretofore available with prior road or bridge geocomposite systemswhere the impermeable barriers are formed at the worksite.

[0047] In accordance with the broadest aspects of the present invention,the geomembrane 18 is a plastic or rubber web. Preferably, the web isselected from the group consisting of polyvinylchloride, a very flexiblepolyethylene, a linear low density polyethylene, a low density linearpolyethylene, an ethylene propylene diene terpolymer, or achlorosuphonated polyethylene and has a thickness in the range of 30 to100 millimeters. More preferably, the geomembrane 18 is an extrudedpolyvinylchloride plastic web with a thickness in the range of 60 to 100millimeters and most preferably, the thickness is substantially 80millimeters. It is generally accepted that a 20 millimeter plastic orrubber membrane is sufficient to provide the impermeable barrier capableof preventing the migration or permeation of moisture or liquid.However, a 20 millimeter membrane provides no margin to protect againstdamage during construction. Thus, the present preferred geomembrane 18inherently provides a margin (50 to 400 percent) against damage duringconstruction, or during repair work, such as resurfacing.

[0048] The geotextile backings 20 and 22 are fabricated of a mat ofnon-woven polyester or polypropylene fibers having a density in therange of 100-400 grams per square meter (g/m²). Most preferably, thegeotextile backings 20 and 22 are non-woven polyester fibers having adensity of 150-200 grams per square member (g/m²). As shown in FIG. 4,the geotextile backings 20 and 22 are heat bonded to the geomembrane 18,preferably just after extrusion, such as by calendaring or rolling underpressure. The preferred range of thickness of the geomembrane 18 isnecessary to accommodate proper bonding, while assuring retention of theproper wicking action in the backings 20, 22.

[0049] Advantageously, the fabricated geocomposite layer 12 may betransported to the construction site on a conventional transport vehicleT in a roll (shown in FIG. 5a), where it is easily unrolled duringconstruction of the road or bridge.

[0050] The road or bridge construction method of the present inventioncan now be explained in more detail. As a first step, the geocompositelayer 12 is formed off-site (see FIG. 4), by a calendaring process, andbrought to construction site on a trailer T (see FIG. 5). The structurallayer 14 of the road or bridge geocomposite system 10 or 40 is preparedin the cut of the ground or on the bridge deck. It is leveled to receivethe geocomposite layer 12. A tack coat C₁ forming a suitable adhesive isapplied, such as by a sprayer E₁ (FIG. 5a). Preferably, the tack coat C₁is an asphalt elastomeric composition. For example, an emulsified,liquid asphalt, which includes bituminous and/or non-bituminouscomponents, can be economically used. The composition selected should becapable of assuring that the geotextile backing 20 is securelymechanically bonded to the upper face of the structural layer 14.

[0051] As shown in FIGS. 5 and 5a, the geocomposite layer 12 is thuslaid onto the upper face of the prepared structural layer 14. Thegeotextile backing 20 advantageously generally conforms to the face, andabsorbs the tack coat C₁ for bonding.

[0052] In the preferred method, an outside force sufficient to insurefull conformity of the geocomposite layer 12 to the structural layer 14,and a more complete absorption of the tack coat C₁, is applied. Theforce may be applied in the form of a conventional road constructionroller R. The roller R thus forces the geocomposite layer 12 intointimate contact with the tack coat C₁ and the structural layer 14 sothat the geotextile backing 20 is now securely adhered to the structurallayer 14.

[0053] Of course, several webs of the geocomposite layer 12 are laid inan abutting end-to-end/side-to-side relationship with overlapping edgesto form a road/bridge section. Next, the geotextile backing 22 isprepared to receive the base layer 16. Specifically, tack coat C₂, thesame as described above, is sprayed on the geotextile backing 22 bysprayer E₂. The base layer 16, for example, is then formed by amechanical paver, and simultaneously bonded to the geotextile backing22. Again, a conventional roller (not shown) used in road construction(see the roller R) finishes the road or bridge deck through compactingthe base layer 16, and in turn pressing the backing 22 into the tackcoat C₂.

[0054] In summary, the results and advantages of the present inventioncan now be fully understood. The road and bridge geocomposite systems 10and 40 include a geocomposite layer 12 having a geomembrane 18 disposedbetween two geotextile backings 20, 22, a structural layer 14 forsupporting the geocomposite layer 12, and a base layer 16 formed on topof the geocomposite layer 12. Advantageously, the geomembrane 18 isimpermeable to block the movement of moisture vertically between thestructural and base layers 14, 16. At the same time, the geotextilebackings 20, 22 are sufficiently porous to provide horizontal wickingaction for the moisture or liquids causing it to move harmlessly to thelateral edges of and away from the road or bridge. Additionally, thegeomembrane 18 is sufficiently flexible and resilient to conform to thelayers 14, 16 of the geocomposite system 10, thereby providing acushioning effect that is operative in increasing the structuralcapacity. As a result, reflective, shrinkage and fatigue cracking andother damage is minimized.

[0055] The foregoing description of a preferred embodiment of theinvention has been presented for purposes of illustration anddescription. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed. Obvious modifications orvariations are possible in light of the above teachings. The embodimentwas chosen and described to provide the best illustration of theprinciples of the invention and its practical application to therebyenable one of ordinary skill in the art to utilize the invention invarious embodiments and with various modifications as is suited to theparticular use contemplated. All such modifications and variations arewith in the scope of the invention as determined by the appended claimswhen interpreted in accordance with breadth to which they are fairly,legally and equitably entitled.

1. A geocomposite system for a road or the like, comprising: ageocomposite layer including an impermeable geomembrane disposed betweenfirst and second geotextile backings; a structural layer for supportingsaid geocomposite layer; and a base layer formed on top of saidgeocomposite layer, whereby the service life is extended through saidgeocomposite layer by increasing the structural capacity and providingprotection against moisture or liquid damage.
 2. The geocomposite systemof claim 1 , wherein said geocomposite layer is bonded to saidstructural layer by said first geotextile backing and to said base layerby said second geotextile backing and substantially conforms to saidstructural layer, whereby reflective, shrinkage and fatigue cracking areminimized.
 3. The geocomposite system of claim 2 , wherein said firstand second geotextile backings have sufficient porosity to providewicking action of liquids laterally along said geomembrane out of saidgeocomposite system.
 4. The geocomposite system of claim 3 , whereinsaid geomembrane is a plastic or rubber web and has a thickness in therange of between 30 and 100 millimeters.
 5. The geocomposite system ofclaim 4 , wherein said geomembrane has a thickness of substantially 80millimeters.
 6. The geocomposite system of claim 4 , wherein saidplastic web is a material selected from the group consisting ofpolyvinylchloride, very flexible polyethylene, linear low densitypolyethylene, low density linear polyethylene, ethylene propylene dieneterpolymer, chlorosuphonated polyethylene and mixtures thereof.
 7. Thegeocomposite system of claim 4 , wherein said plastic web ispolyvinylchloride.
 8. The geocomposite system of claim 1 , wherein saidfirst and second geotextile backings are heat coupled to opposite sidesof said geomembrane.
 9. The pavement system of claim 8 , wherein each ofsaid geotextile backings are fabricated of a mat of non-woven polyesteror polypropylene fibers.
 10. The geocomposite system of claim 8 ,wherein said geotextile is a mat of non-woven polyester fibers.
 11. Ageocomposite system for a bridge or the like, including a deck having anupper surface for supporting the geocomposite system comprising: ageocomposite layer including an impermeable geomembrane disposed betweenfirst and second geotextile backings; a structural layer on the bridgedeck for supporting said geocomposite layer; and a base layer formed ontop of said geocomposite layer, whereby the service life of the bridgeis extended through said geocomposite layer by increasing the structuralcapacity and providing protection from moisture or corrosion damage. 12.The geocomposite system of claim 11 , wherein said geomembrane is aplastic or rubber web; and said first and second geotextile backingshave sufficient porosity to provide wicking action for liquids laterallyalong said geomembrane and out of said geocomposite system.
 13. Thegeocomposite system of claim 12 , wherein said structural layer isreinforced concrete; and said base layer includes a hot-mix asphalt wearsurface.
 14. The geocomposite system of claim 12 , wherein said firstand second geotextile backings are heat coupled to said geomembrane. 15.A method of constructing a geocomposite system for roads, bridges, orthe like having a structural layer, and a base layer, comprising thesteps of: fabricating a geocomposite layer including an impermeablegeomembrane disposed between first and second geotextile backings;preparing the structural layer to receive said geocomposite layer;placing said geocomposite layer with the first geotextile backing inengagement with the structural layer; preparing said second geotextilebacking of said geocomposite to receive said base layer; and formingsaid base layer on said geocomposite layer in engagement with saidsecond geotextile backing, whereby the service life of the road, bridgeor the like is extended through said geocomposite layer by increasingthe structural capacity and providing protection against moisture,liquid damage or deicing solutions.
 16. The method of constructing ageocomposite system of claim 15 wherein the step of forming saidgeocomposite layer includes heat coupling said first and secondgeotextile backings to opposing sides of said geomembrane andsubstantially conforming to said structural layer, whereby reflective,shrinkage and fatigue cracking are minimized.
 17. The method ofconstructing a geocomposite system of claim 16 , wherein the step ofheat coupling includes calendaring said first and second geotextilebackings by applying roller pressure to said opposing sides.
 18. Themethod of constructing a geocomposite system of claim 15 , wherein thestep of preparing the structural layer includes applying a tack coat onsaid structural layer for bonding said geocomposite layer.
 19. Themethod of constructing a geocomposite system of claim 18 , furthercomprising the step of applying a sufficient force to said geocompositelayer to substantially conform the same including said first geotextilebacking to the structural layer, whereby loads are absorbed andtransferred more efficiently through the geocomposite layer to thestructural layer and said backing is coupled to said structural layer.20. The method of constructing a geocomposite system of claim 19 ,wherein the step of applying a force includes rolling said geocompositelayer with a roller.
 21. The method of constructing a geocompositesystem of claim 18 , wherein the step of preparing said secondgeotextile backing of said geocomposite layer to bond to the base layerincludes applying a tack coat to said second geotextile backing.
 22. Amethod of constructing a geocomposite system for roads, bridges, or thelike having a structural layer and a base layer comprising the steps of:fabricating a geocomposite layer including a geomembrane sufficient tosupport the base layer disposed between first and second geotextilebackings, said base layer including an upper portion capable of removaland replacement; bonding said first geotextile backing of saidgeocomposite to the structural layer; forming and bonding said baselayer to said second geotextile backing of said geocomposite; andwherein said upper portion of said base layer may be removed andreplaced without disturbing the bonds between said structural layer,said geocomposite layer, and said base layer.
 23. The method ofconstructing a geocomposite system of claim 22 wherein said upperportion of said base layer forms a wear surface having a thickness of atleast substantially one and a half inches.